1. Field of the Invention
This invention relates to new polyurethane polymers. More particularly, this invention relates to new hydrophilic polyurethane polymers and their application to textile substrates as soil-release, anti-soil redeposition and anti-static agents, and especially to textile substrates containing polyester fibers.
2. Description of the Prior Art
Much research has been directed to the attainment of textile materials having improved soil-release properties. Many of the synthetically produced commercial fibers that are used alone or in blends with each other or incorporated in blends with naturally occurring fibers have a propensity to accept and retain oily grime and dirt. Once the textile material becomes soiled, it is then subjected to a cleaning process for removal of the dirt and/or oily deposits, and only a dry cleaning process will successfully clean the textile material.
The cleaning process normally employed, however, is washing in a conventional home washing machine. In such washing procedures it is virtually impossible to remove the soil and/or oily stains from the textile material, and assuming that the undesirable materials are removed from the textile and/or a fairly clean textile material is being washed, soil remaining in the wash water is redeposited onto the textile material prior to the end of the wash cycle. Hence, when the textile material is removed from the washing machine and subsequently dried, it has not been properly cleaned. Such a condition, heretofore unavoidable, does not satisfy modern requirements in that the textile material after use never again assumes a truly clean appearance, but instead tends to gray and/or yellow due to the soil and/or oily materials deposited and remaining thereon.
The problem heretofore associated with fabrics having synthetic fibers incorporated therein or made entirely of synthetic fibers, has been that the synthetic fibers, as well as being hydrophobic, are oleophilic. Therefore, while the oleophilic characteristics of the fiber permit oil and grime to be readily embedded therein, the hydrophobic properties of the fiber prevent water from entering the fiber to remove contaminants therefrom.
One remedy to the soil removal and soil redeposition phenomenon is to deposit a finish onto the fiber to impart a hydrophilic character to the fiber. Attempts have been made to reduce the oleophilic characteristics of these synthetic fibers by coating the fibers with a coating that is oleophobic, i.e., will hinder the attachment of soil and oily materials to the fibers. Many polymer systems have been proposed which are capable of forming a film around the fibers that constitute the textile material, particularly acid emulsion polymers prepared from organic acids having reactive points of unsaturation. These treating polymers are known as soil-release agents.
The term "soil-release" in accordance with the present invention refers to the ability of the fabric to be washed or otherwise treated to remove soil and/or oily materials that have come into contact with the fabric. The present invention does not wholly prevent the attachment of soil or oily materials to the fabric, but hinders such attachment and renders the heretofore uncleanable fabric now susceptible to a successful cleaning operation.
Concentrated solutions of soil-release polymers have been padded onto fabrics by textile manufacturers to impart a permanent soil-release finish to the fabric. As the amount of soil-release polymer on the fabric is increased, the ability of the fabric to release soil is increased. However, fabrics with this permanent soil-release finish possess many disadvantages. As the amount of soil-release polymer on the fabric is increased the fabric had a tendency to become stiffer and lose the desirable hand characteristic of the fabric. Thus, the upper limit on the amount of soil-release polymer to be used is determined by economics and the resulting adverse effect on the fabric. Fabrics with a heavy application of soil-release polymer do not have the same desirable appearanace and hand as the same fabrics without the soil-release coating. Furthermore, practically speaking, there is a set range of soil-release agent that can be applied, dictated by commercial success.
Some soil-release polymers are effective fabric treating agents even at very low levels on the fabric, at which levels the appearance and hand of the fabric are not adversely affected. Thus, an ideal method of treating a synthetic fiber containing fabric would be to reapply a very small amount of soil-release polymer to the fabric each time the fabric is washed.
Certain polycarboxylate polymers, such as those hydrolyzed acrylamide polymers and certain polymers of methacrylic acid with ethyl acrylate, are very effective soil-release agents at low levels on the fabric. However, these polymers cannot be deposited onto fabrics from dilute solution, as the polymers are so soluble in water that they will not deposit onto the fabric from dilute solution.
Other polymers which have been effective as anti-soil redeposition agents are polyesters containing acid groups or substituent groups which can be water soluble. French Patent No. 1,499,508 describes such polyesters which result from the polycondensation of phthalic acid with a low molecular weight glycol and a polyoxyalkylene glycol to yield polyesters containing hydrophobic units consisting of chains of phthalic acid/low molecular weight glycol and hydrophilic units from the polyalkylene glycol groups. The linking bond between the hydrophobic and hydrophilic units is provided by the ester group formed from an acid group and an alcohol group. The polyester products obtained have a relative viscosity of between 1.1 and 1.5.
There still exists a need in the textile industry for a finishing compound which provides outstanding renewable soil-release, anti-soil redeposition and anti-static characteristics to the textile substrate which is water dispersible and obviates all of the aforementioned disadvantages associated with known soil-release, anti-soil redeposition and anti-static agents.